09C2
Thermal springs
Relationships with habitat classifications. EUNIS: C2.144 Peri-Alpine thermal springs; PAL. CLASS.: 66.74 Peri-Alpine thermal springs.
Conservation status. None.
Category. Nearly Threatened [NT – A2 C1 D2 E2 F1 G2 H3 J L3].
General characteristics. There is a great diversity of natural thermal springs (more than 200), which have high or relatively high temperatures and different quantities of ions of Na, Ca, Fe, Mg, F, S depending on the area where they occur. The depth from which these springs start is an important factor. Their temperature varies between 27–30ºC and 80-90ºC, with alkaline reaction that varies (pH 7,5–9,9). They are of reocrenic type. Their capacity is from 1 dm3/s to 45 dm3/s. The quantity of carbon dioxide (up to 33,7 mg/dm3) or hydrogen sulphide (up to 3–4 mg/dm3) varies. Their bottom is usually stony or clayey. Most of these springs are situated in lowlands, foothills and mountain areas up to 1300 m alt. There are almost no living organisms in the zone close to the sources due to the high-temperature springs with high quantity of hydrogen sulphide. The springs, in which the temperature is lower, particularly those that pass through a karst layer, have bottom faunal complexes. The thermal springs have relatively constant capacity and chemical composition of the water.
Characteristic taxa.
- Plants: Algae – Nostoc spp.;vascular plants – mainly in the places where they enter different water systems: Persicaria amphibia, Polygonum spp., Potamogeton spp.
- Animals: Nematomorpha – Gordius aquaticus, G. interjectus; Crustacea – Gammarus balcanicus, Asselus aquaticus.
Distribution in Bulgaria. Such springs occur mainly on the slopes and in the foothills of Rila Mts. (Sapareva Banya village), Pirin Mts. (Dobriniste, Banya, Dobarsko villages), Rhodopi Mts. (Devin town, Michalkovo village); West and Central Balkan Range, Vitosha Mts. (Zheleznitsa, Knyazhevo, Plana villages) and Lyulin Mts. (Gorna Banya, Bankya villages); West Frontier Mountains (Zemen gorge, Transka Bankya locality); Belasitsa Mts. (Rupite locality); southern Dobrudzha region, etc.
Conservation importance. The thermal springs are important for the regulation and maintenance of the level of the underground water, and thehumidity and mineral composition of the soils in the areas where the water reaches the surface. They change positively the hydrological and hydrochemical parameters of the stagnant or running water bodies in the area of their inflowing.
Threats. Pollution with organic material from waste waters that enter directly into the underground water flow; construction of water catchments, use of the water by water bottling companies. Close to most of the thermal springs there are balneological complexes, hence the existence of natural plant and animal communities are absent. Felling of the trees near the springs has also negative impact. When the water pressure is low and the thermal springs are close to urban areas it is possible that they can be mixed with waste communal waters from damaged water sewage.
Conservation measures taken. A significant part of the thermal springs are under various types of protection as water sources. However, no specific measures for the conservation of the communities that inhabit the springs have been taken. Most of the springs are outside the borders of protected areas. Others are within sanitary-protection territories of water bottling enterprises or catchments for drinking water.
Conservation measures needed. Control on the water quantities that are taken from the springs for household and economic purposes; construction, renovation and maintenance of the sewage systems in the urban areas close to such springs in order to prevent the pollution of the thermal springs with the underground waste water.
References. Vladeva et al. 2000; Illies 1979.
Authors: Jordan Uzunov, Dimitar Kozhuharov
